1. Field of the Invention
The present invention relates to an organic electroluminescent element, and in particular relates to a white light organic electroluminescent element.
2. Description of the Related Art
Recently, with the development and wide application of electronic products, such as mobile phones, PDAs, and notebook computers, there has been increasing demand for flat display elements which consume less electrical power and occupy less space. Among flat panel displays, organic electroluminescent devices are self-emitting, and highly luminous, with wider viewing angle, faster response, and a simple fabrication process, making them the industry display of choice.
Additionally, the organic electroluminescent devices can be used, as not only a light source for liquid crystal displays, but also in the general lighting market. In any case, organic electroluminescent devices have high luminance efficiency and require high operating stability.
As disclosed in U.S. Pat. No. 5,683,823, a white light organic electroluminescent element includes: a anode; a positive-hole transporting layer; a fluorescent emitting layer; an electron transporting layer; and a cathode, wherein the fluorescent emitting layer includes a red light emitting material uniformly dispersed in a blue host emitting material. However, the requirement of a narrow doping concentration range of the red light emitting material in blue host emitting material results in a relatively difficult production process.
As disclosed in European Patent No. 1653783, a white light organic electroluminescent element includes: an anode; a blue emitting layer comprising a blue guest-emitting material doped in a blue host-emitting material; and a yellow/red emitting layer comprising a yellow/red guest-emitting material doped in a blue host-emitting material. However, the energy transfer between the blue host-emitting material and the yellow/red guest-emitting material is not efficient resulting in the reduction of luminance efficiency and stability.
Accordingly, there is a need to develop a white light organic electroluminescent element with high luminance efficiency, high operating stability, and a simple fabrication process.